By default the Windows 8 Developer Preview, which was released last September, is scheduled to expire on 11 March 2012.  After that date the operating system will operate in a limited capacity.

Microsoft has released an update,, that will extend that expiration date for the developer preview to 15 January 2013.  That date should carry the developer preview version of Windows 8 well beyond the expected Release to Manufacturing (RTM) date for the next version of Windows.

Of course, well prior to that new expiration date, the Windows 8 Consumer Preview will be released on 29 February 2012 at an event during the annual Mobile World Congress (MWC) in Barcelona, Spain.

According to the knowledge base article about 14 days prior to this expiration the system will begin reminding you that the preview version is expiring.  Make sure you download this update from Windows Update prior to the expiration date to be sure you have system functionality.  If for some reason you do not get updated prior to that an expired system will shut down every hour and need to be rebooted.  That timeframe should be plenty of time to get the update installed and get you back online.

The best solution to all this expiration stuff is to download the upcoming Windows 8 Consumer Preview on 29 February and see all the improvements that have been made since the developer preview was released.